Method and apparatus for manufacturing panels for vehicles

ABSTRACT

Disclosed herein is a method and apparatus for manufacturing a panel for a vehicle. When a steel sheet is machined to form a panel for a vehicle, a blanking-texturing machine conducts a blanking process for cutting the steel sheet and a texturing process for forming depressions in the steel sheet at the same time. Therefore, the present invention reduces the number of manufacturing processes, thus enhancing the productivity, and reducing the production cost and provides a steel sheet with uniform depressions across the surface of the steel sheet, thereby reducing the coefficient of friction during the pressing process consistently.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims under 35 U.S.C. §119(a) priority to KoreanApplication No. 10-2011-0050085, filed on May 26, 2011, the disclosureof which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to methods and apparatuses formanufacturing panels for vehicles and, more particularly, to a methodand apparatus for manufacturing a panel for vehicles in which when asteel sheet is machined by blanking to form the panel for vehicles,surface of the steel sheet can be textured along with the blanking.

2. Description of the Related Art

Generally, as shown in FIG. 1, manufacturing panels for vehiclesincludes cutting a steel sheet 1 in a shearing process 2 into apredetermined size, machining the cut steel sheet 3 by performing ablanking process 4 into a shape corresponding to a vehicle panel to beproduced, and machining the steel sheet 3 with a pressing process 5.However, because the surface of the steel sheet 3 machined by theblanking process 4 is excessively smooth, friction between the steelsheet 3 and a press punch is increased when the pressing process isconducted because the lubricant used to reduce the coefficient offriction is not easily retained on the excessively smooth surface.Accordingly, the increase in friction reduces the formability of thesteel sheet 3.

Although lubricant is supplied to the steel sheet 3 during the pressingprocess to reduce the coefficient of friction between the steel sheet 3and the press punch, the supplied lubricant cannot be sufficientlyretained by and stored in the steel sheet 3, because the surface of thesteel sheet 3 is excessively smooth. Thus, the lubricant cannoteffectively prevent the coefficient of friction between the steel sheet3 and the press punch from increasing. As a result, there is thedisadvantage of a reduction in the formability of the steel sheet.

In an effort to overcome the above disadvantage, as shown in FIG. 2, atechnique has been proposed in which before the pressing process 5 isexecuted, a rolling process 6 is conducted to form embossments 3 a onthe surface of the steel sheet 3.

In detail, rollers used in the rolling process are plated with chrome.Embossments 3 a are formed on the surface of the steel sheet 3 bypassing the steel sheet 3 between the rollers. When this technique isused, the lubricant supplied to the steel sheet 3 during the pressingprocess is easily retained and stored in spaces between the embossments3 a, thus reducing the coefficient of friction between the steel sheet 3and the press punch, thereby enhancing the formability of the steelsheet 3.

However, in the above-mentioned conventional solution, the shapes of theembossments 3 a are often rendered different depending on the rpm of therollers and the abrasion loss of the chrome that the surface of thesteel sheet 3 was plated with. Hence, the embossments 3 a formed on thesurface of the steel sheet 3 are not uniform. In particular, during thepressing process, the coefficient of friction between the steel sheet 3and the press punch cannot be consistently maintained. Thus, theformability of the steel sheet is still not satisfactory. Moreover, theproduction cost is increased by conducting the rolling process 6 beforethe pressing process 5 and by plating the rollers with chrome.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a method and apparatus for manufacturing a panelfor vehicles in which when a steel sheet that has been cut through ashearing process is machined by blanking to form the panel for avehicle, a plurality of depressions are formed in the surface of thesteel sheet so that lubricant supplied to the steel sheet during apressing process is reliably retained by and stored in the depressions,thus reducing the coefficient of friction between the steel sheet and apress punch during the pressing process, and maintaining the coefficientof friction constant, thereby enhancing the formability of the steelsheet, and reducing the production cost.

In order to accomplish the above object, in an aspect, the presentinvention provides a method for manufacturing a panel for a vehicle,including: blanking-texturing a steel sheet in such a way that when thesteel sheet is cut by blanking into a shape corresponding to the panelfor the vehicle, a plurality of depressions are formed in a surface ofthe steel sheet and then the steel sheet having the depressions ispressed to form the panel for the vehicle.

The depressions may be formed in either of both sides of the steelsheet, and may be formed in both sides of the steel sheet. Each of thedepressions may have a size ranging from about 50 μm to 200 μm. Adensity of the depressions with respect to a surface area of one side ofthe steel sheet may range from about 1% to 20%.

In another aspect, the present invention provides an apparatus formanufacturing a panel for a vehicle, including: a blanking-texturingmachine comprising: a cutting surface for cutting a steel sheet into ashape corresponding to the panel for the vehicle; and a depressionforming portion for forming depressions in a surface of the steel sheetwhen the steel sheet is cut; and a press machining the steel sheethaving the depressions to form the panel for the vehicle.

The blanking-texturing machine may include an upper (top/first) mold anda lower (bottom/second) mold. The cutting surface may be provided on theupper mold. The depression forming portion may be provided on either theupper mold or the lower mold. Alternatively, the depression formingportion may be provided on each of the upper and lower molds.

The depression forming portion may have protrusions for forming thedepressions, and each of the protrusions may have a particle sizeranging from about 50 μm to 200 μm. A density of the protrusions of thedepression forming portion with respect to a surface area of one side ofthe steel sheet may range from about 1% to 20%.

In the present invention, when machining a steel sheet to form a panelfor vehicles, a blanking-texturing machine conducts a blanking processfor cutting the steel sheet and a texturing process for formingdepressions in the steel sheet at the same time. Therefore, the presentinvention reduces the number of manufacturing processes, thus enhancingthe productivity. Moreover, the production cost can be markedly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIGS. 1 and 2 are views illustrating a conventional method formanufacturing a panel for vehicles;

FIG. 3 is a view illustrating method and apparatus for manufacturing apanel for vehicles, according to an exemplary embodiment of the presentinvention; and

FIG. 4 is a view showing depressions formed in a steel sheet byblanking-texturing, according to the exemplary embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention will bedescribed in detail with reference to the attached drawings.

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general such aspassenger automobiles including sports utility vehicles (SUV), buses,trucks, various commercial vehicles, watercraft including a variety ofboats and ships, aircraft, and the like, and includes hybrid vehicles,electric vehicles, plug-in hybrid electric vehicles, hydrogen-poweredvehicles and other alternative fuel vehicles (e.g., fuels derived fromresources other than petroleum). As referred to herein, a hybrid vehicleis a vehicle that has two or more sources of power, for example bothgasoline-powered and electric-powered vehicles.

Panels for vehicles are manufactured by the following processes. Asshown in FIGS. 3 and 4, a steel sheet 1 produced from a steel mill iscut to have a predetermined size through a shearing process 2.Thereafter, the cut steel sheet 3 is machined by a blanking-texturingmachine 10 according to the present invention so that the steel sheet 3is formed in a shape corresponding to a vehicle panel to be manufacturedand, simultaneously, a plurality of depressions 3 a are formed in thesteel sheet 3 during this blanking process in the blanking-texturingmachine. Subsequently, the steel sheet 3 having these depressions 3 a ismachined during a pressing process 5, thus completing the vehicle panel.

The blanking-texturing machine 10 includes an upper (top/first) mold 11and a lower (bottom/second) mold 13. The upper mold 11 has a cuttingsurface 15 which is provided to cut the steel sheet 3. Depressionforming portions 17 are respectively formed on a lower surface of theupper mold 11 and an upper surface of the lower mold 13. The cuttingsurface 15 may be formed on the lower mold 13 rather than on the uppermold 11. However, this may make the operation of cutting the steel sheet3 difficult. Therefore, to facilitate the operation of cutting the steelsheet 3, it is preferable that the cutting surface 15 be formed on theupper mold 11.

Furthermore, the depression forming portion 17 for forming thedepressions 3 a may be formed on either the upper mold 11 or the lowermold 13. Alternatively, the depression forming portions 17 may be formedon both the upper mold 11 and the lower mold 13. In the case when thedepression forming portion 17 is formed on either the upper mold 11 orthe lower mold 13, the depressions 3 a are formed in only one of the twosides of the steel sheet 3. In the case where the depression formingportions 17 are formed on both the upper mold 11 and the lower mold 13,the depressions 3 a are formed in both sides of the steel sheet 3.

It is preferable that the depressions 3 a be formed in both the uppermold 11 and the lower mold 13, because the coefficient of frictionbetween the steel sheet 3 and a press punch can be reduced as much aspossible during the pressing process 5 due to their ability to retain alubricant.

Each depression forming portion 17 has protrusions (not shown) whichform the depressions 3 a on the steel sheet 3. Preferably, the particlesize of each protrusion of the depression forming portion 17 for formingthe depressions 3 a ranges from about 50 μm to 200 μm.

If the particle size of each protrusion of the depression formingportion 17 is about 50 μm or less, the size of each depression 3 aformed in the steel sheet 3 is also about 50 μm or less, thus making itdifficult to retain and store lubricant supplied in the depression 3 aduring the pressing process 5. Thus, the coefficient of friction betweenthe steel sheet 3 and a press punch increases during the pressingprocess. As a result, the formability of the steel sheet 3 deteriorates.On the other hand, if the particle size of each protrusion of thedepression forming portion 17 is about 200 μm or more, the size of eachdepression 3 a formed in the steel sheet 3 is also about 200 μm or more.In this case, there is an advantage in that lubricant supplied duringthe pressing process 5 can be easily held and stored in the depressions3 a, but the strength of the steel sheet 3 may be reduced. Therefore, tosatisfy the ability to keep and store lubricant in the depressions 3 aand maintain the strength of the steel sheet 3, it is preferable thatthe particle size of each protrusion of the depression forming portion17 range from about 50 μm to 200 μm so that the size of each of thedepressions 3 a formed by the depression forming portions 17 also rangesfrom about 50 μm to 200 μm.

Furthermore, the density of the protrusions of the depression formingportion 17 for forming the depressions 3 a is preferably about 1% to 20%of the surface area of one side of the steel sheet 3. If the density ofthe protrusions of the depression forming portion 17 with respect to thesurface area of one side of the steel sheet 3 is about 1% or less, thenumber of depressions 3 a which are formed in the steel sheet 3 is notsufficient. In this case, the amount of lubricant supplied during thepressing process 5 that is held and stored in the depressions 3 a iscomparatively small, thus increasing the coefficient of friction betweenthe steel sheet 3 and the press punch during the pressing process 5. Asa result, the formability of the steel sheet 3 deteriorates.

On the other hand, if the density of the protrusions of the depressionforming portion 17 with respect to the surface area of one side of thesteel sheet 3 is about 20% or more, the depressions 3 a are formed inthe steel sheet 3 such that the density thereof with respect to thesurface area of one side of the steel sheet 3 is also about 20% or more.In this case, although there is the advantage of an increased amount oflubricant being held and stored in the depressions 3 a, the strength ofthe steel sheet 3 may be reduced as the number of depressions 3 aincreases.

Therefore, to satisfy the ability to keep and store lubricant in thedepressions 3 a and maintain the strength of the steel sheet 3, it ispreferable that the density of the protrusions of the depression formingportion 17 with respect to the surface area of one side of the steelsheet 3 ranges from about 1% to 20%. Furthermore, preferably, thedensity of the depressions 3 a formed by the depression forming portion17 also ranges from about 1% to 20% of the surface area of one side ofthe steel sheet 3.

Meanwhile, when the steel sheet 3 that is cut in the shearing process 2is supplied to the blanking-texturing machine 10, the steel sheet 3 isfirst placed onto the depression forming portion 17 of the lower mold13, and the upper mold 11 is thereafter moved downwards onto the lowermold 13. Then, the steel sheet 3 is cut by the cutting surface 15 of theupper mold 11 into a shape corresponding to the vehicle panel (at ablanking step of FIG. 3). Subsequently, when the upper mold 11 isfurther moved downwards, as shown in FIG. 3, the depressions 3 a areformed in the surface of the steel sheet 3 by the depression formingportions 17 of the upper and lower molds 11 and 13 (at a texturing stepof FIG. 3).

As shown in FIG. 4, in an exemplary illustrative embodiment, althoughthe depressions 3 a formed in the steel sheet 3 have been illustrated asbeing circular, the present invention is not limited to this embodiment.In other words, as necessary, the depressions 3 a may have variousshapes, for example, rectangular shapes, rhombic shapes, triangularshapes, etc.

After the blanking-texturing process, the steel sheet 3 having thedepressions 3 a is machined by the pressing process 5 to form a vehiclepanel having the desired shape. When the pressing process 5 isconducted, lubricant is supplied to the steel sheet 3. The lubricantsupplied to the steel sheet 3 is held and stored in the depressions 3 aof the steel sheet 3. When the steel sheet 3 is machined by the presspunch, the lubricant functions to reduce the coefficient of frictionbetween the steel sheet 3 and the press punch.

As described above, in the present invention, when the pressing processis conducted, the coefficient of friction between the steel sheet 3 andthe press punch can be reduced by the lubricant that has been stored inthe depressions 3 a of the steel sheet 3. Furthermore, because thecoefficient of friction between the steel sheet 3 and the press punchcan be consistently maintained during the pressing process, theformability of the steel sheet 3 is enhanced.

In addition, in the conventional technique, the blanking process forcutting the steel sheet and the rolling process for forming thedepressions in the steel sheet must be separately performed. However, inthe present invention, the single blanking-texturing machine 10 conductsthe blanking process for cutting the steel sheet 3 and the texturingprocess for forming the depressions 3 a in the steel sheet 3 at the sametime. Therefore, the present invention reduces the number ofmanufacturing processes, thus enhancing the productivity. Moreover, theproduction cost can be markedly reduced. Furthermore, since thedepressions are all the same size, the lubricant retention is uniformacross the entire surface.

Although the preferred embodiment of the present invention has beendisclosed for to illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A method for manufacturing a panel for a vehicle, comprising:blanking-texturing a steel sheet in such a way that when the steel sheetis cut by blanking into a shape corresponding to the panel for thevehicle, a plurality of depressions are simultaneously formed in asurface of the steel sheet; and pressing the resulting steel sheethaving the depressions to form the panel for the vehicle.
 2. The methodas set forth in claim 1, wherein the depressions are formed in either ofboth sides of the steel sheet.
 3. The method as set forth in claim 1,wherein the depressions are formed in both sides of the steel sheet. 4.The method as set forth in claim 1, wherein each of the depressions hasa size ranging from about 50 μm to 200 μm.
 5. The method as set forth inclaim 1, wherein a density of the depressions with respect to a surfacearea of one side of the steel sheet ranges from about 1% to 20%.
 6. Anapparatus for manufacturing a panel for a vehicle, comprising: ablanking-texturing machine configured to cut a steel sheet into a shapecorresponding to the panel for the vehicle on a cutting surface, andsimultaneously form, by a depression forming portion of theblanking-texturing machine, depressions in a surface of the steel sheetwhile the steel sheet is being cut; and a press machining the resultingsteel sheet having the depressions to form the panel for the vehicle. 7.The apparatus as set forth in claim 6, wherein the blanking-texturingmachine comprises an upper mold and a lower mold, wherein the cuttingsurface is provided on the upper mold, and the depression formingportion is provided on either the upper mold or the lower mold.
 8. Theapparatus as set forth in claim 6, wherein the blanking-texturingmachine comprises an upper mold and a lower mold, wherein the cuttingsurface is provided on the upper mold, and the depression formingportion is provided on each of the upper and lower molds.
 9. Theapparatus as set forth in claim 6, wherein the depression formingportion has protrusions for forming the depressions, each of theprotrusions having a particle size ranging from about 50 μm to 200 μm.10. The apparatus as set forth in claim 6, wherein the depressionforming portion has protrusions for forming the depressions, wherein adensity of the protrusions of the depression forming portion withrespect to a surface area of one side of the steel sheet ranges fromabout 1% to 20%.
 11. A steel sheet for manufacturing a panel vehiclecomprising: a steel sheet cut to correspond to a particular panel forthe vehicle; and a plurality of depressions formed on one surface of thesteel sheet, wherein each of the depressions is formed to be the samesize which ranges from about 50 μm to 200 μm and the plurality ofdepressions have a density of the depressions with respect to a surfacearea of one side of the steel sheet ranges from about 1% to 20%, thedepressions configured to retain lubricant to reduce the coefficient offriction between the steel sheet and a press.